The present invention relates to a headlamp device for bicycles, motorcycles and like vehicles, which is particularly designed to be used for a bulb, powered from a dynamo or from a battery.
Recently, headlamps have been introduced for bicycles and like vehicles adapted to derive power from one or two power sources, such as a dynamo and a battery. However, there is a problem in connection with the positioning of the bulb with respect to the reflector or socket in such headlamp. When the power source is a dynamo of 6 V or a battery of 2.5 V, it is required to use a bulb different in size. Accordingly, when there is no means for adjusting the central position of the bulb filament in a reflector or socket, there is a variation in the axial length of the bulb. When the position of the filament of the bulb is adjusted to be at the focal point of a concave reflected for one size bulb, the light from the bulb proceeds in parallel after being reflected by the reflector and reaches an illumination covering. In such a stae, normal illumination can be achieved. When there is no means for adjusting the position of the bulb filament in the reflector or socket and a larger size bulb is used, the position thereof is out of focus of the reflector, and no normal illumination can be achieved.
To prevent this, it has been proposed to adjust the distance by which the bulb is screwed into the central position of the reflector. With such procedure, however, it is not possible to correctly regulate the axial length of the bulb. In addition, when the bulb is screwed into the reflector an insufficient distance problems arise, such as unstable holding and rattling of the bulb, and poor electrical contact.